http://blog.csdn.net/xceman1997/article/details/7955349
http://www.cnblogs.com/yuyang-DataAnalysis/archive/2012/01/31/2333760.html
http://zhan.renren.com/dmeryuyang?gid=3602888497999161050&checked=true
http://blog.csdn.net/yanqingan/article/details/6125812
原文：http://www.cnblogs.com/pengkunfan/p/4931701.html